A driver's fatigue caused such by driving operation for a long time may increase a risk of a traffic accident. Currently, an apparatus is under development for detecting a driver's degree of fatigue to prevent the traffic accident.
JP-11-314534-A (Page 2, FIG. 7) discloses an apparatus for detecting the driver's degree of fatigue, which identifies a driver, detects a heart rate of the driver and determines the driver's degree of fatigue based on a variation of the heart rate.
However, according to the above-described prior art, the driver's physical condition and/or the daily variation of the driver's physical condition is not taken into account for determining the driver's degree of fatigue. Thus, the apparatus cannot determine the driver's condition with high accuracy. Further, the above-described apparatus includes an ambiguity in determining when to generate an alarm to notify the driver's fatigue.